The present invention relates to pipe couplings, and is an improvement on a cast flange for such couplings housing.
More particularly, the invention provides an improved flange and its seal which is attachable to the external surface of a pipe and which can be used to eliminate a small leak if access to a pipe extremity is available. The flange housing is also useful, again in combination with a seal element, for anchoring an adjacent item and for preventing fluid flow along the external surface of the pipe.
Pipe couplings and the clamps associated therewith are well known and have been manufactured by the present inventors for some years. The coupling comprises a central body member and two side clamps. A prior-art clamp is illustrated in FIG. 1. However there has now been found an improved manufacturing method which at the same time allows a design improvement and cost reduction of this item.
No directly relevant US patents were found. A 2-part seal clamp assembly for piping is disclosed by Friedrich et al. in U.S. Pat. No. 5,692,544, the purpose of which is to contain leakage between the large diameter end flanges of adjoining co-axial pipes. Devices intended to seal pipe leaks are seen in US Patent Applications 2001/0008149 by D{grave over ( )}auria, No. 2004/0108010 by Gaston et al, and No. 2004/0118467 by Pirart. These disclosures do not however relate to the type of seal clamp which is the subject of the present invention.
A disadvantage of presently known end clamps of the steel band type is that the areas adjacent to the lug of the seal clamp, at each side are unflexible, straight and not concave, when viewed parallel to the seal clamp axis, whereas the seal operates better when pressed inwardly by a concave surface. This defect in band clamps could be due to the nature of bending machines, the first and the last portion of a metal strip being curved not being bent, and remaining as flat as the original metal strip, probably because at the beginning and at the end of the bending process the workpiece is in contact with only 2 of the 3 rollers of the bending machine.
In a coupling of the type seen in FIG. 1 of the prior art design, and also in U.S. Pat. No. 4,463,975 to McCord, a sudden increase in thickness of the band when approaching the area of the lug is seen. This thickness results in sharp loss of flexibility near the lug, the outcome of which is that when in use this section will retain its original flat shape and thus fail to conform to the circular seal. More sealing pressure is thus required before a pressure-tight condition prevails. Applying high sealing pressure delays work on site and shortens the life of the flexible seal.